1. Field of the Invention
The present invention relates to a semiconductor device configured with a semiconductor film having a crystal structure formed on a glass substrate, and more particularly, the present invention relates to a semiconductor device for performing the transmission of a signal in the relevant device by means of an optical interconnect.
2. Description of the Related Art
As for a thin film transistor (TFT) formed on an insulating substrate or an insulating film, it is characterized in that its fabricating method is easy comparing to that of a MOS (Metal Oxide Semiconductor) transistor formed on a silicon wafer and it can be fabricated at a low cost using a substrate having a large scale.
Particularly, as for a TFT (THIN FILM TRANSISTOR) (in this case, polycrystalline TFT) whose active layer is formed with a polycrystalline silicon film, since its mobility is larger comparing to a TFT using an amorphous silicon, it is desirable to consider its applications in a wider range of functional devices including not only display devices and photoelectric conversion elements but also the field of integrated circuits.
However, after all, electric characteristics of a polycrystalline TFT have not been comparable to the characteristics of a MOS transistor (single crystal transistor) formed on a single crystal silicon wafer. Particularly, from the viewpoints of ON-state current and mobility, a polycrystalline TFT has been inferior to a single crystal transistor due to the existence of the defaults in the grain boundary when these were compared. Therefore, in case where the preparation of an integrated circuit was attempted using a polycrystalline TFT, the size of a TFT could not be suppressed when a sufficient ON-state current was attempted to obtain. Furthermore, it was difficult to depict a fine pattern on a glass substrate having a large scale at a high rate, and these matters have created a bottleneck in the realization of higher level integration of an integrated circuit.